Variable-speed mechanism.



1. PARKER.

VARIABLE SPEED MECHANISM.

APPLICATION FILED AUG. 21. 1914.

1,196,883.. PatentedSept. 5,1916.

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I. PARKER.

VARIABLE SPEED MECHANISM.

APPLICATION FILED AUG-27' 1914. 1,196,883 Patented Sept. 5,1916.

3 SHEETS-SHEET 3- WITNESSES: I INVENTOR.

BY 77% m '%m 9024 A TTORNE YS.

cause in ury to the "1| STATES PATENTOFFICE.

JOHN PARKER, OF CRANSTON, RHODE ISLAND, ASSIGNOR TO BROWN & SHARPEMANUFACTURING COMPANY, OF PROVIDENCE, RHODE ISLAND, A CORPORATION OFRHODE ISLAND.

Specification of Letters Patent.

Patented Sept. 5, 1916.

Application filed August 27, 1914:. Serial No. 858,977.

To all whom it may concern:

Be it known that I, JOHN PARKER, a subject of the King of Great Britain,residing at Cranston, in the county'of Providence and State of RhodeIsland, have invented certain new and useful Improvements inVariable-Speed Mechanism; and I do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

The invention relates to variable speed mechanism, and more particularlyto means for preventing injury to the mechanism or to the driven oroperating parts of the ma.- chine in case of unusual resistance to theirmovement or operation.

The object of the invention is to provide novel and improved means forpreventing injury to the mechanism or driven parts in the case ofoverload, which is well adapted for use in mechanism wherein widevariations of speed may be secured, and which will operate in a uniformand efficient manner when incorporated in such mechanism. To this endthe invention contemplates the provision in a variable speed mechanismof two connections or couplings constructed to disconnect the drivingpower under an overload, one of the couplings being at or near thedriving end of the train of variable speed gearing, and the other at ornear the driven end of the train of gearing. With this construction thecoupling at or near.the driven end may be constructed to disconnect thedriving power under an overload when the driven partsare being driven atthe lower speeds, while'the coupling at or near the driving end isconstructed to disconnect the driving power under an overload when thedriven parts are being driven at the higher speeds. This enables therequisite driving power to be transmitted through variable speed gearingwhile providing for the automatic disconnection of the driving powerwhenever the driven parts are subjected to an overload sufficient toparts.

the invention outlined The features of above as well as the furtherfeatures of 1nventio'n hereinafter described and set forth in theclaims, will be readily understood from an inspection of theaccompanying drawings and the following detailed desecured to the otherend of the shaft.

scription of the mechanism illustrated thereln.

In the drawings Figure 1 is a side elevat1on of so much of a millingmachine as is v necessary to illustrate the application of the presentinvention thereto; Fig. 2 is a horizontal sect onal view through thevariable speed gearing forming a part of the work feeding mechanism ofthe machine; and Fig. 3 1s a sectional end elevation of the mechanismshown in Fig. 2.

In the drawings the invention is illustrated as embodied in a variablespeed mechanism having substantially the constructlon and mode ofoperation of the mechanism shown and described in Patent No. 794,464,July 11th, 1905. As shown, the varlous parts of the mechanismaresupported by a casing 1 which is secured to the frame 2 of themilling machine; Motion 1S imparted to the gearing included in thevariable speed mechanism through a driving shaft 3 which is mounted toslide longitudinally through its bearings and is provided at one endwith a pinion 4: and near the other end'the gear 5. By sliding the shaftlongitudinally theipinion 4: may be brought lnto engagement with a gear6 secured to one end of a shaft 7 or the gear 5 may be brought intoengagement with a pinio rli 8 he shaft 7 may thus be driven from theshaft 3 at a speed which is either greater or less than the speed of theshaft 3. The shaft 3 may be shifted longitudinally by an operating shaft9, the'rear end of which carries a pinion 1O engaging a rack formed on ayoke 11, the arms of which loosely surround the shaft 3 on oppositesides of a collar 12 secured to the shaft. The front end of the shaft 9is provided with an operating handle 13 and latch pin 14 through whichthe operator may shift the shaft 3 and lock it in either position.

Motion may be transmitted from the shaft 7 to any one of the gears of acone gear 15 througha tumbler gear 16 which engages an elongated pinion17 formed on the shaft 7 and is also arranged to be engaged with any oneof the gears of the cone gear 15. The tumbler gear is mounted to slideupon a shaft 18 carried in the arm of a bracket 19 secured to sleeves 20which surround the shaft 7 and form bearings within which the shaftrotates. The bracket 19 may be rocked to bring the tumbler gear intoengagement with any one of the gears of the cone gear by an arm 21 onone of the sleeves 20 which extends forward toward the front of thecasing and is provided with a handle 22. The arm 21 is held in anyadjusted position by a latch pin 23 arranged to engage a series oflocking holes 24. The tumbler gear is moved laterally on the shaft 18 tobring it into position to register with any one of the gears of the conegear by movement of a slide 25 mounted in the front of the casing andprovided with rearwardly extending arms 26 which embrace the gear. Theslide may be moved to bring the gear into any adjusted position by meansof a handle 27 yieldingly mounted on a stud 28 carried by the slide andarranged to engage any one of the series of locking notches in a lockingplate 29.

Motion is transmitted from the cone gear 15 to the final driven shaft 30of the gear ing through a quill gear 31 keyed to sl ide on the shaft 30and provided with a pinion 32 adapted to engage the largest gear of thecone gear and with a gear 33 adapted to engage one of the smaller gearsof the cone gear. The quill gear may be slid longitudinally on the shaft30 to bring either the pinion 32 or gear 33 into mesh with thecorresponding gear of the cone gear through a shaft 34, the rear end ofwhich is provided with a pinion 35 engaging annular rack teeth formed onthe opposite quill gear. The front end of the shaft 34 is provided witha handle 36 and locking pin 37 by which the operator may shift the quillgear and lock it in either of its adjusted positions. The shaft 30 ofthe variable speed gearing is connected by a Hookes joint 38 with anextensible shaft 39 through which motion is transmitted to the feedmechanism for the work table of the milling machine.

By the mechanism above described the driven shaft 30 of the train ofgearing may be driven at widely varying speeds, some of which may begreater and some of which may be less than the speed of the drivingshaft 3, and thus widely varying feeding movements may be imparted tothe work table. In embodying the referred form of the invention in thisvarlable speed mechanism the Hookes joint 38 is connected with the shaft30 by a shear-pin 40 which is of such strength that it will be shearedoff or give way under a predetermined strain or overload and will thusdisconnect the driving power from the driven parts. It will be apparentthat the comparative strength of the shear-pin which forms the couplingthrough which motion is transmitted to the work table will increase withan increase in the speed of the shaft 30, the driving strength of thiscoupling being the least at the lowest speed and being the greatest atthe highest speed. If the pin, therefore, is made of such strength thatit will give way and thus prevent injury to the parts under a certainoverload when the shaft 30 is driven at the lower speeds, it may be toostrong to give way at the higher speeds under an overload on the drivenparts or operating tools such as would cause injury or breakage. On theother hand, if it is made weak enough to give way under injuriousoverload on the driven parts when the shaft 30 is driven at high speeds,it may be too weak to transmit the proper driving power to the feedtable or other driven parts when the shaft 30 is driven at the lowerspeeds. In accordance with the present invention, asecond coupling ordriving connection is ac cordingly embodied in the train of gearingwhich is constructed to disconnect the driving power when the shaft 30is being driven at the higher speeds and when the driving couplingbetween the driven shaft 30 and the work table has the greatest drivingstrength. This coupling or driving connection is preferably incorporatedin the mechanism through which motion is transmitted to the drivingshaft 3. In the construction shown the shaft 3 is driven through asleeve 41 surrounding one end of the shaft and connected therewith by akey and slot connection. The sleeve 41 is provided with a flange 42carrying a series of spring-pressed coupling pins 43. These pins areprovided with conical or inclined ends engaging corresponding recessesin a sprocket wheel 44 which is loosely mounted on the sleeve 41 and isdriven through a chain from a rotating shaft of the machine. The pins 43are so constructed and the springs back of the pins are of such strengththat the pins will yield or give way under a predetermined strain oroverload and thus disconnect the driving power from the driven parts.This coupling or driving connection has the greatest driving strengthwhen the driven shaft 30 is being driven 'at its lowest speed and isimparting the .slowest feeding movements to thework table, since at thistime the speed of the shaft 3 is the highest as compared with the speedof the shaft 30. The driving strength of the coupling decreases as thespeed of the shaft 30 increases and is the least when the shaft 30 isbeing driven at its highest speeds, at which times in the constructionshown the shaft 3 is rotating at a lower speed than the shaft 30. Thetwo driving couplings may therefore be so proportioned that theshear-pin 40 will give way under overloads on the driven parts when theparts are being driven at low speeds while the driving pins 43 will giveway under similar overloads when the work table is being fed at thehighest speeds. The proper driving power may therefore be transmittedthrough the variable speed gearing while provision is made forautomatically disconnecting the driving power incase undue resistance isoffered to the movement of the driven parts.

While it is preferred to employ the form of driving couplings orconnections shown and described, it will be understood that bothcouplings may be of the same construction or that other forms ofcouplings or driving connections which will operate to throw out thedriving power under overload, either by giving way or otherwise, may beemployed without departing from the invention. It will also beunderstood that additional couplings or driving connections constructedto disconnect the driving power may be incorporated in the variablespeed gearing if found desirable, although two such couplings willusually be found-suflicient to secure the desired results in a practicaland satisfactory manner. will also be understood that the particularlocation of the couplings or driving connections is not essential andmay be varied as found desirable or best suited to the form of variablespeed mechanism in which the invention is to be incorporated.

Having explained the nature and object of the invention and specificallydescribed one form of machine in which it may be embodied, what I claimis:

1. Variable speed mechanism, having, in combination, driving and drivenmembers, mechanism for effecting variations in speed between saidmembers, a coupling through which motion is transmitted to the drivingmember constructed to disconnect the driving power under an overloadwhen the driven parts are being driven at high speeds, and a couplingthrough which motion is transmitted from the driven member constructedto. disconnect the driving power under an overload when the driven partsare being driven at low speeds.

2. Variable speed mechanism, having, in combination, driving and drivenmembers,

mechanism for efl'ecting variations in speed 4 between said members, acoupling through under an overload when the driven parts are beingdriven at low speeds.

3. Variable speed mechanism, having, in

combination, driving and driven members,

intermediate gearing through which the driven member maybe driven atvarying speeds both higher and lower than the speed of the drivingmember, a coupling through which motion is transmitted to the drivinmember constructed to disconnect the drlving power under an overload,and a coupling through which motion is transmitted from the drivenmember constructed to disconnect the driving power under an overload.

*4. Variable speed mechanism, having, in combination, driving and drivenmembers, variable speed gearing through which the driven member may bedriven at widely varying speeds, a coupling through which motion istransmitted to the driving mem ber constructed to disconnect the drivingpower under an overload when the driven parts are being driven at highspeeds, and a coupling through which motion is trans mitted from thedriven member constructed to disconnect the driving power under anoverload when the driven parts are being driven at low speeds.

5. Variable speed mechanism, having, in combination, driving and drivenmembers and intermediate mechanism for effecting variations in speedbetween said members,

and a"pluralit of driving connections constructed to dlsconnect thedriving power only under overloads, the relative driving strengths ofwhich vary at different speeds.

. JOHN PARKER.

Witnesses:

LUTHER D. BURLINGAME, W. T. LIDDALL.

